2 NaN3 + 2 HNO2 → 3 N2 + 2 NaOH + 2 NO
This is an oxidation-reduction (redox) reaction:
2 N-1/3 - 14/3 e- → 2 NII (oxidation)
6 N-1/3 - 2 e- → 6 N0 (oxidation)
2 NIII + 2 e- → 2 NII (reduction)
2 NIII + 6 e- → 2 N0 (reduction)
NaN3 is a reducing agent, NaN3 is a reducing agent, HNO2 is an oxidizing agent, HNO2 is an oxidizing agent.